While sailing lawfully up the Yangste in 1949, the British warship Amethyst found its return to the open sea blocked by Communist Chinese shore batteries that unexpectedly opened fire. In charge, Lietenant Commander Kerans was not however prepared for his crew and his ship to remain as a hostage for the Chinese to use as an international pawn.

Richard Todd
as Lieutenant-Commander John Simon Kerans

William Hartnell
as Leading Seaman Leslie Frank

Akim Tamiroff
as Colonel Peng

Donald Houston
as Lieutenant Weston

Keye Luke
as Captain Kuo Tai

Sophie Stewart
as Miss Charlotte Dunlap

Robert Urquhart
as Flight Lieutenant Fearnley

Richard Leech
as Lieutenant Strain

Barry Foster
as Petty Officer McCarthy

Thomas Heathcote
as Mr. Monaghan